The diagnostics and monitoring of structures, such as that carried out in the structural health monitoring field, are often accomplished by employing arrays of sensing elements. While many advances have been made, the field continues to be challenged by an increased need to develop “smart” systems. For example, purely passive systems exist for detecting impacts and other load changes. However, these systems often do little more than detect the presence of such load changes, with any diagnosis or further analysis being left to other systems.
In contrast, purely active systems exist that are capable of querying a structure to determine its dynamic characteristics, but these active systems also suffer from their own drawbacks. For instance, active systems must constantly query the structure, resulting in wasted energy and expense when they are not needed. It is therefore desirable to combine active and passive systems in structural health monitoring, so as to simultaneously bring forth the advantages of both systems.
Furthermore, because each of these systems often requires large numbers of sensors in order to be effective, structures often must have a variety of sensing elements placed at various locations. Because individual sensing elements must often be placed separately, affixing a large array of such sensing elements can be tedious and time consuming. In addition, as each individual sensing element can require one or, commonly, multiple wires, large arrays of sensing elements can require a large number of individual wires, which may be difficult to handle and keep track of. The securing of such large numbers of wires can often be painstaking and time consuming, as well. It is therefore further desirable to combine active and passive sensors, and their wires, together in such a manner that the abovementioned difficulties are avoided, or at least reduced.